Permanent & Induced Magnets (Edexcel IGCSE Physics)

Spec point — 6.5 · know that magnetism is induced in some materials when they are placed in a magnetic field

Permanent & induced magnets

Magnetic materials

Magnetic materials are attracted to a magnet; non-magnetic materials are not

• Magnetic materials are materials which are attracted by magnets

  • Being a magnetic material does not mean the material is itself a magnet

• Very few metals in the periodic table are magnetic, these include:

  • Iron
  • Cobalt
  • Nickel

• Steel is an alloy which contains iron, so it is also magnetic

• Magnetic materials will always be attracted to the magnet, regardless of which pole is held close to it

Magnetic materials attracted to either pole of a magnet

• To test whether a material is a magnet it should be brought close to a known magnet

  • If it can be repelled by the known magnet then the material itself is a magnet
  • If it can only be attracted and not repelled then it is a magnetic material

• There are two types of magnets

  • Permanent magnets
  • Induced magnets

Permanent magnets

• Permanent magnets are made out of permanent magnetic materials, for example steel

• A permanent magnet will produce its own magnetic field

  • It will not lose its magnetism

Induced magnets

• When a magnetic material is placed in a magnetic field, the material can temporarily be turned into a magnet.

  • This is called induced magnetism

• When magnetism is induced in a material:

  • One end of the material will become a north pole
  • The other end will become a south pole

• Magnetic materials will always be attracted to a permanent magnet

  • This means that the end of the material closest to the magnet will have the opposite pole to magnets pole closest to the material

Inducing magnetism in a magnetic material

• When the magnetic material is removed from the magnetic field it will lose most/all of its magnetism quickly

Worked Example The diagram below shows a magnet held close to a piece of metal that is suspended by a light cotton thread. The piece of metal is attracted towards the magnet.

Which of the following rows in the table gives the correct type of pole at X and the correct material of the suspended piece of metal?

	Type of pole at X	Material of suspended metal
A	North	Nickel
B	South	Nickel
C	North	Aluminium
D	South	Aluminium

Answer: A

• X must be a north pole

  • The piece of metal is being attracted towards the magnet
  • The law of magnetism states that opposite poles attract

• The material of the suspended piece of metal is nickel

  • Nickel is a magnetic material (It will experience a force when it is placed in a magnetic field, in this case it is attracted towards the magnet)

• B is incorrect because X cannot also be a south pole (and hence is a north pole)

  • If the pole at X was a south pole then the piece of metal would be repelled from the magnet because the law of magnetism states that like poles repel

• C and D are incorrect because aluminium is not a magnetic material

  • A non-magnetic material would be unaffected by the magnetic field produced by the magnet.